Jetson Memory Audit

Read-only memory-focused snapshot for a Jetson, plus the drop_caches verify-loop helper that confirms freed memory actually shows up as free instead of cached.

Purpose

Measure current Jetson memory consumers, capture before/after baselines, and verify whether user-approved changes actually reclaimed DRAM. Use live device data rather than estimates from container size, model size, or generic process memory.

CRITICAL: Memory appears stuck after stopping vLLM / sglang (JetPack below 7.2 / L4T below r39.0)

This is the most common memory confusion on Jetson releases before JetPack 7.2 or before L4T r39.0.

After you stop a vLLM, sglang, or Ollama server (or any CUDA workload), the memory shown as free by free -h or tegrastats may not recover — even though the process is gone. nvidia-smi may also show misleadingly low free GPU memory.

Root cause: The Thor RM (resource manager) holds freed sysmem pages in its own pool after a CUDA context exits. On Unified Memory Architecture (UMA) devices like Jetson, cudaMemGetInfo reads RM pool state and reports far less free memory than is actually available to a new process.